# US 12,113,509 B2 · Acoustic wave device with IDT electrode including al metal layer and high acoustic impedance metal layer

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,113,509 B2
- Document ID: US12113509B2
- Status: Granted
- Kind: B2
- Application number: 17/482,660
- Filed: 2021-09-23
- Published: 2022-01-13
- Granted: 2024-10-08
- Earliest claimed: 2019-04-04
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Shou Nagatomo; Katsuya Daimon
- Web page: https://patentgrep.com/patent/US12113509B2

## CPC

- H03H 9/02574: {of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate}
- H03H 9/25: Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)}
- H03H 9/02559: {of lithium niobate or lithium-tantalate substrates}
- H03H 9/02866: {of bulk wave excitation and reflections}
- H03H 9/14541: {Multilayer finger or busbar electrode}
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

An acoustic wave device includes an energy confinement layer, a piezoelectric layer made of Y-cut X-propagation lithium tantalate having a cut angle in a range from about −10° to about 65°, and an IDT electrode. Electrode fingers of the IDT electrode include an Al metal layer and a high acoustic impedance metal layer having a Young's modulus equal to or more than about 200 GPa and an acoustic impedance higher than Al. The high acoustic impedance metal layer is closer to the piezoelectric layer than the Al metal layer. A wavelength specific film thickness tLT of the piezoelectric layer is expressed by tLT≤1λ. The total of normalized film thicknesses obtained by normalizing the film thickness of each layer of the electrode finger by a density and Young's modulus of the Al metal layer satisfies T≤0.1125tLT+0.0574.

## Claims

### Claim 1

An acoustic wave device comprising:
an energy confinement layer;
a piezoelectric layer on the energy confinement layer and made of Y-cut X-propagation lithium tantalate having a cut angle of equal to or more than about −10° and equal to or less than about 65°; and
an IDT electrode on the piezoelectric layer; wherein
the IDT electrode includes a plurality of electrode fingers, the plurality of electrode fingers including a multilayer body including an Al metal layer defined by an Al layer or an alloy layer including Al, and a high acoustic impedance metal layer that has a Young's modulus equal to or more than about 200 GPa and a higher acoustic impedance than an acoustic impedance of Al;
the high acoustic impedance metal layer is closer to the piezoelectric layer than the Al metal layer;
when a wavelength defined by an electrode finger pitch of the IDT electrode is denoted by λ and a wavelength specific film thickness of the piezoelectric layer is denoted by tLT, tLT≤1λ is satisfied; and
a total of normalized film thicknesses obtained by normalizing a film thickness of each layer of the plurality of electrode fingers by a density and a Young's modulus of the Al metal layer is denoted by T, the expression T≤0.1125tLT+0.0574 is satisfied.

### Claim 2 (depends on 1)

The acoustic wave device according to claim 1, wherein the Al metal layer is an Al layer, and a film thickness of the Al metal layer is equal to or more than about 85 nm.

### Claim 3 (depends on 1)

The acoustic wave device according to claim 1, wherein
the energy confinement layer includes a high-acoustic-velocity material layer; and
an acoustic velocity of a bulk wave propagating through the high-acoustic-velocity material layer is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer.

### Claim 4 (depends on 3)

The acoustic wave device according to claim 3, wherein
the energy confinement layer includes a low-acoustic-velocity film between the high-acoustic-velocity material layer and the piezoelectric layer; and
an acoustic velocity of a bulk wave propagating through the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer.

### Claim 5 (depends on 3)

The acoustic wave device according to claim 3, wherein the high-acoustic-velocity material layer is a high-acoustic-velocity support substrate.

### Claim 6 (depends on 4)

The acoustic wave device according to claim 4, further comprising:
a support substrate; wherein
the high-acoustic-velocity material layer is a high-acoustic-velocity film provided between the support substrate and the low-acoustic-velocity film.

### Claim 7 (depends on 1)

The acoustic wave device according to claim 1, further comprising:
a support substrate, wherein
the energy confinement layer is an acoustic reflection film provided on the support substrate;
the acoustic reflection film includes a high acoustic impedance layer having a relatively high acoustic impedance and a low acoustic impedance layer having a relatively low acoustic impedance, the high acoustic impedance layer and the low acoustic impedance layer being alternately laminated; and
the piezoelectric layer is provided on the acoustic reflection film.

### Claim 8 (depends on 1)

The acoustic wave device according to claim 1, wherein the piezoelectric layer has a film thickness of equal to or more than about 0.05λ and equal to or less than about 0.5λ.

### Claim 9 (depends on 8)

The acoustic wave device according to claim 8, wherein the piezoelectric layer has a film thickness of equal to or more than about 0.05λ and equal to or less than about 0.35λ.

### Claim 10

An acoustic wave device comprising:
an energy confinement layer;
a piezoelectric layer on the energy confinement layer and made of Y-cut X-propagation lithium tantalate having a cut angle of equal to or more than about −10° and equal to or less than about 65°; and
an IDT electrode on the piezoelectric layer; wherein
the IDT electrode includes a plurality of electrode fingers, the plurality of electrode fingers including a multilayer body including an Al metal layer defined by an Al layer or an alloy layer including Al, and a high acoustic impedance metal layer that has a Young's modulus equal to or more than about 200 GPa and a higher acoustic impedance than an acoustic impedance of Al;
the high acoustic impedance metal layer is located closer to the piezoelectric layer than the Al metal layer;
the high acoustic impedance metal layer is an Mo layer, a W layer, or an Ru layer;
the following Expression 2 is satisfied; and
a combination of each coefficient of Expression 2 and a metal of the high acoustic impedance metal layer is a combination shown in Table 1 below:
a0(2)(tLT−c0)2+a0(1)(tLT−c0)+b0≤aLT(2)(tLT−cLT)2+aLT(1)(tLT−cLT)+aM(2)(T−cM)2+aM(1)(T−cM)+dLT-M(tLT−cLT)(T−cM)+b Expression 2;
TABLE 1
METAL FORMING HIGH ACOUSTIC IMPEDANCE
METAL LAYER
COEFFICIENT
Mo
W
Ru
a0(2)
12315.2368
a0(1)
2360.5990
c0
0.2250
b0
6287.8999
aLT(2)
−54656.6400
−57176.4500
−51809.7600
aLT(1)
12799.3184
10774.6530
13577.4784
cLT
0.2250
0.2250
0.2250
aM(2)
−256136.5936
−252048.6950
−177802.3113
aM(1)
−22623.1348
−15612.4350
−22797.2384
cM
0.0844
0.0851
0.0816
dLT-M
0.0000
72370.3153
0.0000
b
6481.5295
6416.9953
6416.0623

### Claim 11 (depends on 2)

The acoustic wave device according to claim 2, wherein the Al metal layer is an Al layer, and a film thickness of the Al metal layer is equal to or more than about 85 nm.

### Claim 12 (depends on 10)

The acoustic wave device according to claim 10, wherein
the energy confinement layer includes a high-acoustic-velocity material layer; and
an acoustic velocity of a bulk wave propagating through the high-acoustic-velocity material layer is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer.

### Claim 13 (depends on 12)

The acoustic wave device according to claim 12, wherein
the energy confinement layer includes a low-acoustic-velocity film between the high-acoustic-velocity material layer and the piezoelectric layer; and
an acoustic velocity of a bulk wave propagating through the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer.

### Claim 14 (depends on 12)

The acoustic wave device according to claim 12, wherein the high-acoustic-velocity material layer is a high-acoustic-velocity support substrate.

### Claim 15 (depends on 13)

The acoustic wave device according to claim 13, further comprising:
a support substrate; wherein
the high-acoustic-velocity material layer is a high-acoustic-velocity film provided between the support substrate and the low-acoustic-velocity film.

### Claim 16 (depends on 10)

The acoustic wave device according to claim 10, further comprising:
a support substrate; wherein
the energy confinement layer is an acoustic reflection film provided on the support substrate;
the acoustic reflection film includes a high acoustic impedance layer having a relatively high acoustic impedance and a low acoustic impedance layer having a relatively low acoustic impedance, the high acoustic impedance layer and the low acoustic impedance layer being alternately laminated; and
the piezoelectric layer is provided on the acoustic reflection film.

### Claim 17 (depends on 10)

The acoustic wave device according to claim 10, wherein the piezoelectric layer has a film thickness of equal to or more than about 0.05λ and equal to or less than about 0.5λ.

### Claim 18 (depends on 17)

The acoustic wave device according to claim 17, wherein the piezoelectric layer has a film thickness of equal to or more than about 0.05λ and equal to or less than about 0.35λ.